Directly esterified fatty acyl isethionate (DEFI) is produced by the direct esterification of an alcohol of formula:HOR′SO3M with an organic acid (e.g. fatty acid) of formula:RCOOH to produce a surface acting agent (i.e., DEFI) of formula:RCOOR′SO3M where R is a monovalent aliphatic hydrocarbon radical having 7 to 24, preferably 8 to 22 carbon atoms; R′ comprises divalent aliphatic hydrocarbon radicals containing 2 to 4 carbons; and M is an alkali metal cation, particularly sodium, potassium or lithium; or an ammonium cation. In the reaction to make DEFI, the alcohol and organic acid noted above are reacted in the presence of a catalyst in order to accelerate and produce commercially viable yields.
Surface active agents are one of the basic raw materials in the detergent industry. Specifications for such materials generally require the absence of colored impurities in order to prepare high quality, aesthetically pleasant, formulated products such as detergent bars. Absence of colored impurities also minimizes the chances of imparting off-odors to formulated products. Thus, it is obviously desirable to use catalysts which do not cause color impurities when catalyzing the DEFI reaction. It is further desirable to use DEFI catalysts which provide good reaction rates as well as not leaving undesirable corrosivity toward stainless steel used in DEFI reactors.
U.S. Pat. No. 3,320,292 to Cahn et al. discloses catalysis of DEFI using zinc oxide, zinc soap or mixtures. Group 4 metal catalysts of the subject invention provide far superior reaction rates when used in comparable amounts with zinc oxide.
U.S. Pat. No. 4,405,526 to Lamberti discloses catalysis of DEFI using a mixture of zinc oxide and an organic sulfonic acid.
Unexpectedly, applicants have now found that Group 4 metal (defined by the well known Periodic Table of the Elements according to IUPAC convention, new notation) based compounds catalyze the reaction of DEFI faster and more cheaply compared to commercially known catalysts (e.g., zinc oxide). Further, the reaction with these catalysts do not lead to corrosion or color disfiguration problems at catalytic levels. Using these catalysts, it is thus possible to enhance reaction kinetics, increase production capacity of DEFI and reduce manufacturing costs.